Gripper control for sheet-fed rotary printing presses

ABSTRACT

A gripper control for a sheet-fed printing press includes a shaft on which an impression cylinder is mounted. A cam is mounted on the shaft and the cam operates an actuating means to provide an oscillating motion to a gripper means for feeding sheets to the press in synchronism with the rotation of the shaft. Spring means are provided to apply a biasing force to the oscillating motion of the gripper means, and control means are provided to control the spring force dependent on the rotation of the shaft.

United States Patent 1 Jahn [ Dec. 30, 1975 GRIPPER CONTROL FORSHEET-FED ROTARY PRINTING PRESSES [75] Inventor: Hans-GeorgJahn,Wieslock,

Germany [73] Assignee: Heidelberger Druckmaschinen AG,

Heidelberg, Germany [22] Filed: May 23, 1973 [21] Appl. No.: 363,043

[30] Foreign Application Priority Data May 23, 1972 Germany 2224732 [52]US. Cl. 101/232; 101/408; 271/277 [51] Int. C1. B65H 5/10 [58] Field ofSearch 271/268, 277; 101/408-412, 232, 246

[56] References Cited UNITED STATES PATENTS 834,107 3/1952 Kolland101/409 2,767,653 10/1956 Babicz 101/409 2,776,136 1/1957 Dietrich....101/408 2,926,909 3/1960 Jantzen 271/268 2,991,072 7/1961 Dietrich101/409 3,151,552 l0/1964 101/246 3,257,109 6/1966 271/268 3,385,5975/1968 101/411 3,412,995 11/1968 271/268 3,463,484 8/1969 Rudolph101/409 FOREIGN PATENTS OR APPLICATIONS 1/1963 Canada 271/268 PrimaryExaminer.1. Reed Fisher Attorney, Agent, or Firm-Herbert L. Lerner [57]ABSTRACT A gripper control for a sheet-fed printing press includes ashaft on which an impression cylinder is mounted. A cam is mounted onthe shaft and the cam operates an actuating means to provide anoscillating motion to a gripper means for feeding sheets to the press insynchronism with the rotation of the shaft. Spring means are provided toapply a biasing force to the oscillating motion of the gripper means,and control means are provided to control the spring force dependent onthe rotation of the shaft.

2 Claims, 6 Drawing Figures U.S. Patent Dec. 30, 1975 'Sheet1of23,929,069

US. Patent Dec. 30, 1975 Sheet 2 of2 3,929,069

F'ig. h

Fig.5

Fig.6

GRIPPER CONTROL FOR SHEET-FED ROTARY PRINTING PRESSES This inventionrelates to a gripper control for sheetfed, rotary printing presses. Moreparticulary the invention relates to a gripper control of the type inwhich a cam is mounted on a shaft and drives a hollow shaft supportingthe gripper mechanism in an oscillating manner by means of a cam rollerand a drive linkage. A pretensioned torsion spring which biases the camroller against the cam by means of the drive linkage is accommodated inthe hollow shaft.

Cam-controlled gripper drives are known in which the grippers are swungor operated in a form-locking manner by means of auxiliary cams.However, these known drives are very expensive and are justifiable onlyfor printing presses handling large sheet sizes.

Cam-controlled gripper drives are also known in which a cam roller isheld in positive engagement with a cam by means of a spring. These knowndrives have the disadvantage that due to the large angle of oscillationof the grippers, large spring excursions or expansion are produced whichresult in spring forces that have an unfavorable effect on the drivemechanism. The maximum speed of the printing press as well as itsproneness or tendency to produce striping are strongly influenced by theabove-mentioned characteristic of the spring forces.

In other known gripper drives, attempts have been made to correct theabove-mentioned disadvantages and shortcomings by providing particularlylong, soft springs which requires less applied forces to effectcontraction and expansion. However, due to space limitations, such longsprings cannot be accommodated in all printing machines. Althoughgripper drives are also known which operate with short, strong springs,such known drives must co-control the spring engagement point by meansof a second cam so that the spring forces do not rise excessively. Theadditionally required cam mechanism for controlling the spring forcesrequires a considerable expenditure.

Accordingly, it is an object of the present invention to overcome thedisadvantages of the aforementioned prior art arrangements and toprovide for keeping the spring forces within a range favorable for thefunctioning of the gripper drive by utilizing means which are not largeand which require little space.

The aforementioned object is achieved by providing a torsion springhaving one end which is fastened to a bearing shaft and which isrotatably disposed in a hollow shaft. The bearing shaft protrudes fromthe hollow shaft and is provided with an eccentric cam. A chain isconnected to the curve segment of the eccentric cam closest to the axisof symmetry of the bearing shaft. The chain is connected to a crankmounted on a shaft in such a manner that the chain is wound onto orunwound from the eccentric cam during each back and forth rotation ofthe hollow shaft.

By providing the eccentric cam on the bearing shaft, a rise in thetension of the torsion spring during the back and forth movement of thegrippers can be avoided almost completely. As a result it is possible toincrease the transporting speed of the gripper substantially.

Other featurcswhichare considered as characteristic not intended to belimited to the details shown, since variousmodifications and structuralchanges may be made therein without departing from the spirit of theinvention and within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however,together with additional objects and advantages thereof will be bestunderstood from the following description of specific embodiments whenread in connection with the accompanying drawings, in which:

FIG. 1 is a schematic representation illustrating the operation of agripper drive according to one embodiment of the invention.

FIG. 2 is a top view, partly in section, of the gripper driverepresented in FIG. 1.

FIG. 3 is an elevational view of the spring compensation arrangement ofthe gripper drive.

FIG. 4 is a time-travel diagram or graph in which the degrees of arc areplotted on the abscissa and the angle of rotation of the drive lever andbearing shaft are plotted on the ordinate.

for the invention are set forth intlie appended claims?- Although theinvention is illustrated and described in relationship to specificembodiments, it is nevertheless FIG. 5 is a diagram or graphrepresenting the difference between the angles of rotation of the drivelever and the bearing shaft.

7 FIG. 6 is a diagram or graph representing the spring characteristicsof the torsion spring.

Referring to the drawing, there is shown in FIG. 2 a single-revolutionshaft 1 of an impression cylinder 2. A control cam 4 is provided on thedrive side of the printing press in front of a drive gear 3 for drivinga gripper mechanism. The shaft 1 of the impression cylinder 2 issupported in sleeve bearings 5 and 6 in the side walls 7 and 8respectively, of the printing press. A cam roller 9, which is rotatablymounted on a roller lever 10, runs on or follows the control cam 4. Theroller lever 10 is fulcrumed at a bearing post 11 which is supported onthe side wall 7. The roller lever 10 is attached or operativelyconnected to a drive lever 13 by means of a link 12. The drive lever 13is firmly connected to a plug 14 which closes off the longitudinal endof a hollow shaft 15 and is firmly connected with the shaft 15.

The hollow shaft 15 carries a gripper bar 16 by means of two fulcrumedlevers 17 and 18 and is supported in the side walls 7 and 8 by sleevebearings 19 and 20 respectively. Inside the hollow shaft 15 thereextends a torsion spring 21, one end of which is attached to thepreviously mentioned plug 14 and the other end of which is firmlyconnected with a bearing shaft member 22. This bearing shaft 22 isarranged rotatably in needle bearings 23 at that end of the hollow shaft15 which faces away from the plug 14. The free end of the bearing shaft22, which protrudes from the hollow shaft 15, is equipped with aneccentric circular cam 24 as best may be seen in FIG. 3. The cam 24 isarranged eccentrically to the axis of symmetry 25 of the bearing shaft22. In the part of the curve of the cam 24 which is closest to the axisof symmetry 25, there is fastened a chain 26. The chain 26 is fastenedin such a manner that it is wound up and down on the curved andeccentric surface 27 of the circular cam 24 when the bearing shaft 22rotates or rocks back and forth. The other end of the chain 26 isconnected with a crank 28 which is secured or pinned to the end of theshaft 1 of the impression cylinder 2 which protrudes from the center ofthe bearing of-thesidewalls 8 as shown in FIG n I During one revolutionof the impression cylinder 2,

the roller lever 10 and thereby also the drive lever 13 is swung, due tothe design of the cam 4, from the solid to the dashed position (FIG. 1)and back again. In this process the gripper bar 16 executes a movementtoward a non-illustrated feed table and then moves back again to theimpression cylinder 2 with a gripped sheet. The torsion spring 21 ispretensioned and therefore causes the cam roller 9 to be always pressedor biased against the running or operating surface of the control cam 4by means of the drive lever 13, the link 12, and the roller lever 10.The crank 28 which also rotates with the impression cylinder 2 causesrotation of the bearing shaft 22 via the chain 26 in such a manner thatthe pretension of the torsion spring 21 changes only little, or not atall, during the stroke of the gripper bars 16.

The change of the pretension of the torsion spring 21 during theoperating cycle can be varied as desired by appropriate design of thecurved surface 27 of the cam 24. The possibility exists furthermore toadjust the pretension of the torsion spring 21 by adjusting the cam 24on the bearing shaft 22.

The manner of operation of the gripper drive with gripper compensation,according to the invention, will now be explained with reference toFIGS. 4 to 6.

FIG. 4 shows a time-travel diagram in which the time t in degrees of arcis plotted on the abscissa and the rotation angles or of the drive lever13 and B of the bearing shaft 22, respectively, are plotted on theordinate.

The angle of rotation travelled by the drive lever 13 per unit time isshown by the curve c, while the curvef represents the angle of rotationof the bearing shaft 22. At the time t,, for example, the drive lever 13has travelled through the angle of rotation a, while at the same time,the bearing shaft 22 has been rotated through the angle [3,. At thisinstance, the difference of the angles of rotation is therefore a, B 7that is, the pretension of the torsion spring 21 has increased slightly,as the drive lever 13 leads the bearing shaft 22. When the gripper bars16 swing back, however, the bearing shaft 22 leads, so that again aslight increase of the pretension of the torsion spring 21 occurs. Onlyat the reversal points, that is, when the sheet is taken over or passedon by the grippers, does the pretension correspond approximately to thepredetermined magnitude. This continuous increase and decrease of theangle 7, the difference between the angles of rotation of the drivelever 13 and the bearing shaft 22, is shown in FIG. 5.

In FIG. 6 the spring characteristic h of the torsion spring 21 is shownwherein the torque is represented as a function of the spring excursionor twist, that is, the angle of rotation or angle of torsion of thetorsion spring 21. a is the twist of the torsion spring 21 for thepretension torque M If the bearing shaft 22 did not co-rotate during theoperating cycle, further torsion of the torsion spring 21 by the angleof rotation 01 would result in addition to the pretension. Accordingly,the torque produced by the torsion spring 21 would increase to MHowever, because the bearing shaft 22 does co-rotate through the crank28 and the chain 4 26, only a slight additional torsion by an angle 'yoccurs, so that the torque actually produced by the torsion spring 21increases maximally only to M Due to the gripper motion and theco-rotation of the bearing shaft 22 via the supplementary drive 26, 28,24, there results at the points of greater acceleration or deceleration,a slight increase of the pretension of the torsion spring 21, as thediagrams according to FIGS. 4 to 6 shown, while at those points wherethe acceleration and deceleration corresponds approximately to the value0, practically only the preset pretension is effective. As a consequenceof the above in the acceleration and deceleration phases, the lifting ofthe cam roller 9 from the control cam 4 is prevented by the slightincrease of the torsion forces. This fact, as well as the avoidance of alarger rise of the torsion forces, permits substantially highertransport speeds of the gripper drive than would be the case without thespring compensation according to the invention. Because of theapproximately uniform stress of the torsion rod or rods, the margin ofsafety against breakage is considerably increased.

I claim:

1. Gripper control means for sheet-fed printing presses, comprising ashaft on which an impression cylinder is mounted, oscillatably mountedgripper means for feeding sheets to the printing press, a cam mounted onsaid shaft, actuating means operatively connected between said cam andsaid gripper means to oscillate said gripper means by said cam and saidactuating means upon rotation of said shaft, spring means connected tosaid actuating means to apply a spring force to the oscillating motionof said gripper means, and control means connected to said spring forcontrolling said spring force, said control means being connected tosaid shaft, wherein said gripper means includes a hollow shaft, saidacutating means including a lever arrangement operable by said cam foroscillating said hollow shaft, and said spring means comprises a torsionspring extending in said hollow shaft, a bearing shaft memberoscillatably mounted in said hollow shaft, said torsion spring havingone end thereof attached to said bearing shaft member, said controlmeans including a mechanical connection between said bearing shaftmember and said impression cylinder shaft, said mechanical connectioncomprising a crank mounted on said shaft, a chain attached to saidcrank, an eccentric cam mounted on said bearing shaft member, said chainbeing attached to said cam at the curved segment of the latter closestto the axis of symmetry of said bearing shaft member, said chain beingarranged on said cam in such a manner that the chain is wound on and offof said eccentric cam for each oscillation of said bearing shaft.

2. A gripper control according to claim 1 including bearing meansrotatably supporting said bearing shaft member in said hollow shaft,said bearing shaft protruding from the end of said hollow shaft, saideccentric cam being mounted on said protruding end of said bearing shaftmember.

UNITED sTATEs PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTIONPATENTNO.: 29,069 DATED 1 December 30, 1975 mvrzmorars) HANS-GEORG JAHNit is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

In the heading to the printed specificatien with respect to ForeignApplicatien Priority Data at line 10,

"May 23, 1972 Germany........222 r732", should read 23, o I a q I o cSigned and Scaled this A ttes t:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner of Patentsand Trademarks

1. Gripper control means for sheet-fed printing presses, comprising ashaft on which an impression cylinder is mounted, oscillatably mountedgripper means for feeding sheets to the printing press, a cam mounted onsaid shaft, actuating means operatively connected between said cam andsaid gripper means to oscillate said gripper means by said cam and saidactuating means upon rotation of said shaft, spring means connected tosaid actuating means to apply a spring force to the oscillating motionof said gripper means, and control means connected to said spring forcontrolling said spring force, said control means being connected tosaid shaft, wherein said gripper means includes a hollow shaft, saidacutating means including a lever arrangement operable by said cam foroscillating said hollow shaft, and said spring means comprises a torsionspring extending in said hollow shaft, a bearing shaft memberoscillatably mounted in said hollow shaft, said torsion spring havingone end thereof attached to said bearing shaft member, said controlmeans including a mechanical connection between said bearing shaftmember and said impression cylinder shaft, said mechanical connectioncomprising a crank mounted on said shaft, a chain attached to saidcrank, an eccentric cam mounted on said bearing shaft member, said chainbeing attached to said cam at the curved segment of the latter closestto the axis of symmetry of said bearing shaft member, said chain beingarranged on said cam in such a manner that the chain is wound on and offof said eccentric cam for each oscillation of said bearing shaft.
 2. Agripper control according to claim 1 including bearing means rotatablysupporting said bearing shaft member in said hollow shaft, said bearingshaft protruding from the end of said hollow shaft, said eccentric cambeing mounted on said protruding end of said bearing shaft member.